D'Lite conversion to #0102

[Mark]

Here is a few pictures of the amp I'm building.

[IMG766]http://i149.photobucket.com/albums/s69/ ... CN4783.jpg[/img]
[IMG766]http://i149.photobucket.com/albums/s69/ ... CN4782.jpg[/img]
[IMG766]http://i149.photobucket.com/albums/s69/ ... CN4781.jpg[/img]
[IMG766]http://i149.photobucket.com/albums/s69/ ... CN4780.jpg[/img]

It still has a way to go and the blue tape is to hold the teflon wires in place till they develop a "memory" and want to stay where they are.

Critique?

[jelle]

Mark, looks good from my cell phone! Switcheable mid cap...Teflon coax...nice!

[Mark]

Thanks Jelle, the mid cap is switchable, a resistor is in the circuit so the effective pot value changes from 250K to 100K. Of course I have to decide between log and linear.

The hi cut on the overdrive is switchable too. The master volume pull switch controls that.

I changed the D'Lite layout as I wanted a bit more real estate for the daughter board and the presence circuit. I didn't like the fact it was earthed to the pre-amp power supply. I wanted it to go back to it's own node.

The amp also has a choke over the resistor. I wonder how the output transformer will perform over a Fender Bassman style output transformer. There is a noticeable size difference between them. The original Heybour does sound pretty good though.

I was also mindful about the current capability of the feedback loop. The original 6.2K/390 value shows Moss and Norm were also concerned the amp sounded too stiff.

Just a few thoughts about it all, and I've thought about it for quite a while.

[Mark]

It's going and I've played through it. It sounds very good with my Les Paul. I'm at the odds and sods stage where I'm playing and determining bias, looking for any issues and listening to the amp.

A feature I like in the amp is the foot switchable mid boost. It works great for soloing when playing clean (increase in volume and a fatter tone) it is also great for soloing when using the overdrive same again fatter tone and louder. PAB also makes the amp louder, but it makes the tone brighter, the mid boost does the opposite and it really adde to the capabilities of the amp.

I have to give it to Moss and Norm, it is a worthy addition to a Dumble style amp. I'm wonder why more guys here aren't experimenting with this.

[Mark]

I've working through a few issues.

1. Some noise on the wiper of the master volume pot. So far I think I'm looking at vibration being picked up by the cable.

I messed around with this wire, it was actually louder and noisier when in free air. I was going to route the wire under the relay PCB, but there were so many other wires there, I thought the risk of oscillation was too great. I also didn't hear a tonal difference from the short co-ax run. I put the co-ax in and the amp is going great (noise wise.)

2. The presence/negative feedback loop doesn't appear to be working very well.

I'm tossing up between sticking with the 8.2K NFB resistor and the 1K resistor versus replacing them with the 4.7K NFB resistor and the 390 ohm resistor.

3. The tone of the amp doesn't appear to be all that smooth. I'm thinking of looking at those 250pF caps. I don't see any reason they should be the same value.

Still thinking and tweaking.

[Structo]

Hi Mark,

Regarding the Presence circuit, did you wire it the Brown Note way or the Dumble way?
I know that Scott was after Moss for the way they made their layout as not being the Dumble way. Check out #124 for the correct way.

I think on lower power amps the feedback resistor is larger, so for 2x 6L6 or 2x 6V6 a 6.2K or 8.2K might sound better.

For 4x 6L6 the 4K7 seems to be the one.

I did a lot of tweaking on my D'lite before I was happy.

For the OD channel, try 270pf-330pf, you can make the B side the larger one to smooth the exit.

How is your bass response?

If you find it gets too woofy you can do the pre-OD entrance mod with a .05uF before the 220K. To make that even more clear bypass that cap with a 4M7.

Also might want to wait until you get some hours on the amp and tubes to let things settle down.
I chased my own tail not following that advice.

[Mark]

Thanks for the reply Structo.

The amp is wired per Tony's #0102 layout diagram.

The bass response is much better after the changes, I think the highs would be smoother with a more effective NFB loop.

The snubbers are quite tricky, 270pF sounds good with humbuckers but not so good with single coils. Thus the hi cut tone control is switchable for the single coils. At the moment I'm using a 0.001uF cap but I'm finding that it is too subtle, 0.01uF seems right to me. It should have good range with a 1 meg pot.

I don't think the amp needs the entrance mod, I'm finding the amp sounds a little ragged (without the Dumbleator).

I'm thinking the NFB loop with more current will tighten up the amp particularly in the highs. I'm after yacht rock smoothness!

[Mark]

I settled on a 3.3K feedback resistor, it worked well, though I think I could have used anything as low as 1.5K and gotten good results.

Upon turning the amp on, I found it is very easy to get a bad OD sound out of this amp, and once the amp is dialled in the OD sound is quite pleasing and somewhat unforgiving.

I had thought of replacing the 270pF snubbers with 330pF snubbers, but once the amp is dialled in that doesn't seem necessary.

The Dumbleator is a real joy with this amp and it can sort out some unruly OD tones. The 68pF cap on the master volume comes into it's own with the Dumbleator in use.

This amp only pulls 37 watts, but it is loud enough to get complaints from the family, and it still has some volume in reserve. The 100 watt must be REAL LOUD!

[IMG766]http://i149.photobucket.com/albums/s69/ ... CN4790.jpg[/img]
[IMG766]http://i149.photobucket.com/albums/s69/ ... CN4791.jpg[/img]
[IMG766]http://i149.photobucket.com/albums/s69/ ... CN4792.jpg[/img]

[Structo]

Mark how did you do the front panel on the Dumbleator?

Looks real sharp.

[Teleguy61]

"The 100 watt must be REAL LOUD!"

Yes.
Yes, it can be.
Definitely.

[Mark]

Hi Tom

It is a very large sticker. I had a local company Signarama do it. I just had to specify all the dimensions and font types.

It is going to be a hassle putting it into a 19 rack case, washers will be necessary.